1. Field of the Invention
This invention relates to the hydroxylation of olefins. In particular, it relates to a procedure for reacting an olefin, e.g. ethylene and propylene, with an organic hydroperoxide oxidant in the presence of a specific catalyst composition to produce the corresponding glycol.
2. Description of the Prior Art It is well known from the technical literature, including patents, that olefins can be effectively oxidized with osmium oxide compounds, particularly osmium tetroxide, to their corresponding diols when the reaction is carried out with catalytic amounts of osmium tetroxide and a stoichiometric amount of a strong co-oxidizing agent.
More specifically, Japanese patent application No. Sho 54-145604, published Nov. 14, 1979, is directed to a process for hydroxylating olefins in the presence of OsO.sub.4, a quaternary ammonium salt co-catalyst such as tetra ethyl ammonium bromide, and a peroxide including organo peroxides and H.sub.2 O.sub.2 as the oxident. Selectivities to glycol of from about 4.5 to about 66% are disclosed. It is to be noted, however, that the critical component of the co-catalyst as implied in this patent is the quaternary ammonium cation rather than the particular identity of the anion, since the anion can be any of halogen, hydroxy, nitrate, perchlorate, sulfate, methane sulfonate, trifluoromethane sulfonate, and tetra fluoro borate ions, while the cation must always be quaternary ammonium. In contrast, the present invention recognizes that it is the identity of the anion which is critical, the critical anion being a halogen.
U.S. Pat. No. 2,414,385 discloses the use of hydrogen peroxide and a catalytically active oxide, such as osmium tetroxide, dissolved in an essentially anhydrous, non-alkaline, inert, preferably organic, solvent, to convert, by oxidation, unsaturated organic compounds to useful oxygenated products such as glycols, phenols, aldehydes, ketones, quinones and organic acids. The formation of glycols is achieved by conducting the reaction at temperatures of between several degrees below 0.degree. C. and 21.degree. C. Such low reaction temperatures drastically, and disadvantageously, reduce the reaction rate to commercially unacceptable levels. At temperatures greater than 21.degree. C., the formation of aldehydes, ketones and acids is favored.
U.S. Pat. No. 2,773,101 discloses a method for recovering an osmium containing catalyst such as osmium tetroxide, by converting it to the non-volatile osmium dioxide form, distilling the hydroxylation product, re-oxidizing the osmium dioxide to the volatile osmium tetroxide, and then recovering the same by distillation. Suitable oxidizing agents used to oxidize olefins, and re-oxidize the osmium dioxide, include inorganic peroxides such as hydrogen peroxide, sodium peroxide, barium peroxide; organic peroxides, such as t-butyl peroxide or hydroperoxide, benzoyl peroxide; as well as other well known oxidizing agents such as oxygen, perchlorates, nitric acid, and chlorine water. As with other methods of the prior art, the above process yields undesirable by-products (see col. 1 line 55) thus reducing the selectivity of the process.
U.S. Pat. No. 4,049,724 describes the preparation of glycols from alkenes and from unsaturated alcohols in an aqueous system using osmium tetroxide and specifying stable and water-soluble aliphatic hydroperoxides, such as tert-butyl hydroperoxide, while a critical pH of 8 to 12 is maintained by a suitable combination of alkali metal buffering compounds. The preparation of propylene glycol utilizing tert-butyl hydroperoxide is exemplified in the patent at a selectivity based on the hydroperoxide of 45 percent.
See also, K. B. Sharpless in JACS, Mar. 31, 1976, pp. 1986-7 which discloses that whereas alkaline solutions of hydrogen peroxide decomposed violently in presence of OsO.sub.4, solutions of t-butyl hydroperoxide in the presence of base (tetraethylammonium hydroxide gave yields superior to that obtained with sodium or potassium hydroxide) and OsO.sub.4 were stable and provided good yields of vicinal diols from a variety of olefins.
Recently, U.S. Pat. No. 4,203,926 discloses the heterogeneous catalysis of ethylene and propylene to the corresponding glycol in a process in which ethylbenzene hydroperoxide is reacted with the olefin in a two-phase liquid (organic-aqueous) reaction system in the presence of osmium tetroxide and cesium, rubidium or potassium hydroxide. This two-phase system requires organic soluble hydroperoxides and appears specific for ethylbenzene hydroperoxide.
None of the above references disclose the halogen ion containing co-catalysts of the present invention.